Surprise when taking off the cylinder
 

I pulled apart my engine because the cam end plug started leaking pretty badly and I knew it needed rings because it burns oil. Other then that the bike was great, a little down on power but would run all day. No horrible noises and once it was warmed up it purred.

I pulled off the head and the piston was sitting halfway and the bore looked better then expected (40k miles). I pulled off the jug anyway and saw this... Wtf is going on here???

http://imagizer.imageshack.us/v2/102...0/706/40nl.jpg
Large Version Here

Slight shiny area from piston slap
http://imagizer.imageshack.us/v2/102...0/835/ixh5.jpg

The piston didn't have any abnormal wear and the rings weren't broken or mangled. The oil ring was a little stuck but that was it, the rest of the engine looks almost brand new internally and the oil is always clean (no glitter). The gunk/water spots are from degreasing it last night.

Is it just really crappy machining from the factory or something worse? There isn't any rod knock and just some minor tapping from the top end when cold which goes away after a few mins.

Haha no, I'm just one of the possibly many owners. I put about 18,000 miles on it since I bought it last summer.

I had someone say they look like factory tooling chatter marks, I'd think so too because if the piston did that it would look pretty mangled (plus it's horizontal scoring only). I definitely think someone did a hone and new rings sometime in the past, the top end looked like it had been opened and they managed to strip one of the valve cover bolts in the process.

Either way it's going to get a +1 bore and a new piston. I just hope that I can find a shop to measure it for me, or my digital calipers are accurate enough to see if it's a stock piston or larger. I don't wanna buy a new one that's too small...

I wonder, cant you buy the inside sleeve and replace you dont have to bore?

Perhaps the piston was siezed at some point? Perhaps the bike was left outside, and the piston/cylinder slightly corroded together..?

Just a guess.

A re-bore is a lot cheaper than you think....

I don't think you can buy the sleeves for an XT600. I don't know anyone who makes/sells them. Please tell me if you know differently...

I've take the barrel to an engine place and get a re-bore.

Just think of the power increase ;) 0.3HP maybe !! :smartass:

This website has been going FOREVER it seems. Taught me a lot when I was starting out.

Dan's Motorcycle "Pistons, Cylinders & Rings"

Yamaha Tenere 600 95 98mm Wiseco Cylinder Sleeve 84 96 | eBay

http://www.ebay.com/itm/Wiseco-Cylin...cadbdf&vxp=mtr

Great news..... Cheap too.

Last sleeve I had changed only cost me £100. And you can just use stock piston/rings too.

Yes i think its a good deal, specally for people that dont have anyone near that can rebore.

Changing a sleeve is no easy task without a good puller and a BIG press though either.

I've not ever bothered myself..

I've known people to chisel out the old sleeve... :eek3:

KEDO - Performance Products has sleeves aswell. They have the up to 98mm sleeve, and a bigbore aswell :thumbup1:

Boring it is going to be the more cost effective route for me, I was getting quotes for ~$60 including honing. A ProX piston is about $100 and then I'll be replacing the rear spring for a hyperpro, a bunch of leaky o-rings, gaskets and regular maintenance stuff.

I was thinking about the JE piston but 11.5:1 seems too high, I'd rather have the bike be reliable. Plus it would need cams, better carbs, etc and I'd rather just use that for putting towards my 1190 Adventure dream bike :biggrin:

A friend of mine who has done a million or so bore jobs says:

"Marks look like cutter chatter from a previous bore job, maybe in a back yard in India? 0.2 on 1-10 scale."

So the bad news is it may already be on the first oversize. Check the top of the piston, usually will have a size stamp if oversize.

You could also hone that smooth then measure it... Then check a manual for the piston clearance.. You might be okay with standard piston and oversized rings... New sleeve is the best long term solution and as your already doing a rebuild I think its worth the extra hundred ...

I got the cylinder measured and it's at 95.6mm. It's an odd size to be at but the machinist said at least it's straight. I'll be getting a 96mm ProX piston and getting it bored and honed next week.